Cylinder block for two-cycle engines



Nov. 10, 1959 E. c. KIEKHAEFER 2,911,965

CYLINDER BLOCK FOR TWO-CYCLE ENGINES Original Filed Aug. 12, 1953 2Sheets-Sheet 1 IN VEN TOR. 7 6 340F646 er" BY $4M. SM 15 Stu u.filler/rem.

Nov. 10, 1959 E. c. KIEKHAEFER 2,911,965

CYLINDER BLOCK FOR TWO-CYCLE ENGINES Original Filed Aug. 12, 1953 2Sheets-Sheet 2 IN VEN TOR.

a a 9M 9 M filo/ways United States Patent CYLINDER BLOCK FOR TWO-CYCLEENGINES Elmer C. Kiekhaefer, Cedarburg, Wis.

Original application August 12 1953 Serial No. 373,73. Divided and thisapplicatioli Januhry 13, 1958, 561131 No. 708,520

4 Claims. (Cl. 123-7 3) This invention relates to two-cycleinternal-combustion engines and particularly to the method of formingthe transfer passage and intake ports of the cylinder for effecting thedirectional control of the fuel mixture into the cylinder and morecomplete scavenging of the engine.

The invention provides a preformed sleeve cast within a cylinder blockwith a transfer passage formed therein to extend approximately to thecenter of the intake ports which are thereafter drilled in the block toform corresponding channels at the end of the transfer passage and whichdirect the fuel mixture into the cylinder.

An object of the invention is to'simplify the manufacture of thecylinder blocks for internal-combustion engines.

Another object is to provide for the more controlled flow of the fuelmixture into the cylinder so that the-re is obtained a more completescavenging or clearing of the cylinder of the exhaust gases.

Another object is to provide guide means for the directional control ofthe fuel mixture through the ports of the cylinder sleeve and support ofthe sleeve between the ports referred to.

Another object is to increase the volumetric efficiency of the engineand the better flow of the fuel mixture through the transfer passage.

These and other objects and advantages will be more fully set forth inthe following description of an embodiment of the invention illustratedin the accompanying drawings.

In the drawings:

Figure 1 is a plan view of the engine with parts of the crankcase andcylinders broken away and sectioned;

Figure 2 is an elevation of the base of one of the cylinder shown inFigure 1 as taken on line 22 of Figure 1;

Figure 3 is a section taken .on line 33 of Figure 2 before the port isformed in the cylinder;

Figure 4 is a view similar to Figure 3 showing the port as formedtherein and completed; and

Figure 5 is a section taken on line 5-5 of Figures 2 and 4.

The engine 1, shown in the drawings, includes the crankcase 2 whichcarries one end of the crankshaft 3 in the bearings 4. The valve unit 5closes the corresponding opposite end of crankcase 2 and is secured bythe air intake member 6 which carries a carburetor, not shown, andprovides for the introduction of a fuel mixture from the carburetor tothe crankcase chamber 7. The pistons 8 are connected to the oppositethrows 9 of crankshaft 3 by the rods 10 for reciprocation in opposedrelation.

Each cylinder block 11 is provided with a cast-iron sleeve 12 which iscast within the block and carries the corresponding piston 8 forreciprocation therein. The base flange 13 of each cylinder block 11 isprovided with a planiform face 14 which is adapted to be bolted againstthe corresponding opposite faces of crankcase 2. The inner end of eachsleeve 12 projects from flange 13 into the crankcase and opens in to thecrank chamber 7. The outer end of each cylinder block 11 is fitted witha threaded opening to receive the base of the spark plug 15 and isotherwise closed to provide a combustion chamber 16. The series ofradially formed fins 17 are cast integrally withveach cylinder block 11and provide for cooling of the cylinder by air passing exteriorlythereover.

In the operation of the engine, the pistons 8 move simultaneously inopposite directions to effect compression of the fuel mixture within thecombustion chamber 16 of each cylinder. During such movement, valve unit5 is open to allow the fuel mixture which includes air at atmosphericpressure to enter the crank chamber 7 through air intake member 6.During the power stroke of each piston 8 effected by the simultaneous.combu,s tion of the fuel charges in chambers 16, the pistons movetoward each other to compress the fuel mixture within the crankcasechamber 7. Towards the end of the power stroke of the pistons, the ports18 in cylinder blocks 11 are uncovered by pistons 8 and opened toreceive the initial exhaust of the burned gases from the respectivecombustion chambers 16. Shortly thereafter, the ports 19 'of thecylinders are similarly uncovered by pistons 8 to provide for thecommunication of the respective chambers 16 with crank chamber 7 throughthe corresponding transfer passages 29. With the opening of ports 19,the compressed fuel mixture within the crank chamber enters chambers 16of the cylinders and displaces the exhaust gases remaining therein andrefills the chambers 16 with a fuel charge.

According to the invention as shown in the drawings, each passage 20 isformed as a recess in each block 11 on each side of sleeve 12. Eachrecess opens from face 14 of the respective block alongside the sleeveof the block.

Each recess providing a transfer passage 20 is formed by a core, notshown, which extends from the base of the cylinder alongside sleeve 12and up to the location of ports 19. The inner end face 21 of each recessis formed angularly with respect to the sleeve as shown in Figure 3 tocoincide with the centerlines of ports 19.

The cross-section of each passage 20 as formed by the core decreasesfrom the base of cylinder block 11- to ports 19 which facilitateswithdrawal of the core. The decreasing cross-section results in anacceleration of the fuel mixture as it travels the length of the passagefrom crank chamber 7 to ports 19.

The face 21 defining the upper end of the passage is formed by a core todefine an .acuate angle with the outside of sleeve 12. The anglereferred to is generally determined by the desired angularity of thestream of fuel mixture to enter the combustion chamber 16 through ports19 which are formed by drilling after the casting of the cylinder block11 has been completed and the core forming the passage has beenwithdrawn.

The ports 19 are formed by drilling at spaced loca tions on center lineswhich coincide generally with end face 21 of the recess so that in theprocess of drilling the ports, the several corresponding channels 22 areformed in the block 11. Each channel is separated by the portions 23 ofthe block remaining therebetween.

The larger circular recesses 24 are formed in the outer portion of block11 concentrically of the drilled holes to receive the plugs 25 which areseated in recesses 24 to close the outer holes formed in block 11 indrilling ports 19, as described.

The ports 19 may be accurately located with respect to the end face 21of transfer passage 20 by tool means, not shown, which may be indexedrelative to the face 14 of base flange 13.

Passage 20 is of decreasing cross-section from face 14 of block 11 tothe end 21 of the passage and extends immediately adjacent to sleeve 12so that the fuel mixture which passes over the sleeve directly cools theadjacent portions of the sleeve.

The fuel mixture reaching the end of each passage 20 enters channels 22and is deflected and directed thereby through the corresponding ports.Liquid particles carried in the fuel mixture and reaching the end ofpassage 20 are similarly deflected through ports 19 into the cylinder sothat no accumulation of liquid fuel is allowed to develop.

The fuel mixture is directed through the ports with a less turbulentflow and in generally straight lines of flow. The construction advocatedby the present invention provides that the wall thickness of the portionof the ports on the transfer passage side of end face 21 is limited tothe thickness of the sleeve 12 providing a more direct flow of the fuelmixture into the combustion chamber 16.

The precise angular direction, location and size of each port may beselected to attain the desired scavenging and recharging characteristicsfor the engine cylinder.

This application is a division of abandoned application, Serial No.373,783, filed August 12, 1953, and entitled, Cylinder Block forTwo-Cycle Engines and Method for Making the Same.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. In a cylinder block for a two-cycle internal-combustion engineincluding a crankshaft carried by a crankcase and a piston connected tothe crankshaft for reciprocation; said cylinder block comprising awear-resistant sleeve having a combustion chamber at one end thereof andadapted to support the piston for reciprocation therein, the other endof said sleeve being open and communicating with the chamber of saidcrankcase, said block surrounding said sleeve and having an endcorresponding to the crankcase end of the sleeve secured to the enginecrankcase and provided with at least one recess adjoining said sleeveand communicating with said crankcase chamber, said recess having aninner end face provided with a number of channels in predeterminedradial relation to the axis of the said sleeve and of circular section,said block further including a series of corresponding inner and outerholes respectively aligned with the corresponding channels and extendingthrough the block and sleeve, said inner holes forming ports whereby thefuel mixture from the crankcase passing to the end of said recess intosaid channels is directed by the channels through said ports into saidcombustion chamber, and means closing said outer holes.

2. The invention of claim -1 wherein the block is provided with a recesson opposite sides of the sleeve and said channels together with thecorresponding ports in said sleeve have projected axes whichsubstantially intersect at a location within the sleeve more remote fromthe end of the sleeve communicating with the crankcase chamber than saidports.

3. In a cylinder block for a two-cycle internal-combustion engineincluding a crankshaft carried by a crankcase and a piston connected tothe crankshaft for reciprocation; said cylinder block comprising awear-resistant sleeve having a combustion chamber at one end thereof andadapted to support the piston for reciprocation therein, the other endof said sleeve being open and communicating with the chamber of saidcrankcase, said block surrounding said sleeve and having a correspondingend secured to the engine crankcase and provided with at least onerecess immediately adjoining said sleeve and communicating with saidcrankcase chamber, said recess having an inner end face including anumber of ribs defining channels therebetween and in predeterminedangular relation to the axis of the said sleeve, said block furtherincluding a series of corresponding inner and outer holes respectivelyaligned and extending through the block and sleeve, said channels andthe inner holes being in accurate alignment, said inner holes formingports whereby the fuel mixture from the crankcase passing through saidrecess is directed by the channels into the combustion chamber of thesleeve, the ribs defining said channels extending into said recess tosupport the portions of the sleeve between the ports thereof.

4. In a two-cycle internal-combustion engine including a crankshaftcarried by a crankcase and a piston connected to the crankshaft andemploying crankcase induction and precompression of a fuel mixture, acylinder block confining a wear-resistant cylindrical sleeve having acombustion chamber at one end thereof and communicating with thecrankcase chamber at the other end thereof and adapted to support thepiston for reciprocation therewithin, said block surrounding said sleeveand having an end corresponding to the crankcase end of the sleevesecured to the crankcase and provided with at least one recessimmediately adjacent said sleeve and communicat ing with said crankcasechamber, said recess having a decreasing cross-section in the directionaway from the crankcase to provide for acceleration of fuel mixturepassing therethrough to the sleeve combustion chamber and terminating inan end face forming an acute angle relative to the sleeve, said blockfurther including a plurality of spaced circular bores extending throughthe block and its sleeve to provide a series of inner and outer openingsin said block, said bores having their respective axes disposed tocoincide generally with the end face of the recess and intersecting saidrecess to form corresponding arcuate channels in the end face, the inneropenings of said bores forming ports whereby the fuel mixture from thecrankcase passing through the recess and directed by the channels isadmitted to the combustion chamber, and means closing said outeropenings.

References Cited in the file of this patent UNITED STATES PATENTS2,331,554 Irgens Oct. 12, 1943 2,705,481 Bakke et al. Apr. 5, 19552,740,390 Irgens Apr. 3, 1956

